The invention is based on a device for driving a wiper arm as generically defined by the preamble to claim 1.
Wiper systems with a plurality of windshield wipers for motor vehicles are fastened with their wiper bearings to the vehicle body directly or indirectly via a mounting plate. The mounting plate or a tubular mounting platexe2x80x94if the wiper carrier also has tubular hollow profilesxe2x80x94includes a motor mounting plate, which has a wiper drive mechanism with a wiper motor and a gear mounted on it. A power takeoff shaft of the gear is supported in a gear dome and, as a rule via a crank and connecting rods, drives further cranks, which are connected solidly to one drive shaft for each windshield wiper.
It is also possible for the drive shaft of the wiper motor to drive a four-bar lever mechanism. The four-bar lever mechanism has a drive lever, which is seated pivotably on a drive axis and is connected pivotably via a coupling rod to a drop arm. The drop arm is seated pivotably on a stationary shaft. A fastening part of a wiper arm is integrally formed onto the coupling rod and together with it forms a so-called four-bar wiper lever, to which the hinge part of the wiper arm is fastened via a foldaway hinge. The drive lever can be driven directly by a power takeoff shaft of the wiper motor or via a crank and connecting rods. It can also be embodied as a cross lever. The kinematics of the four-bar lever mechanism produce a combined reciprocating and swiveling motion of the windshield wiper. As a result, the windshield wiper is better able to follow the angular contour of a vehicle window.
A wiper blade with a support bracket system and a wiper strip is pivotably connected to the wiper arm. For a good outcome of wiping and to avoid chattering, it is important that the wiper strip with its wiper lip be guided over the vehicle window at a certain approach angle. Although the production tolerances of the individual, numerous components of the windshield wiper and its drive mechanism are only slight, still the sum of the tolerances, together with those of the fastening to the vehicle body and of the vehicle body itself, is so great that an optimal approach angle is not assured in mass production. While the wiper systems, because of their high ratio of length to width, are well oriented crosswise to the vehicle direction, poor orientation results above all in the longitudinal direction of the vehicle.
According to the invention, the fastening part is separably fastened to the coupling rod and can be adjusted relative to the coupling rod about a displacement axis, extending in the longitudinal direction, in a displacement region. As a result, the fastening part and with it the wiper arm with its wiper blade can be adjusted about its longitudinal axis, so that the wiper strip during assembly is given its optimal approach angle to the windshield, regardless of production tolerances of the vehicle.
The coupling rod is expediently screwed to the fastening part between the hinges and, in the axial direction on both sides of the fastening position, has guide faces, on which the fastening part rests. As a result, the bending forces that are transmitted from the wiper blade to the fastening part are favorably absorbed by the coupling part. To keep the pressure per unit of surface area between the guide faces and support faces low, it is advantageous that numerous guide faces, which produce a wide support spacing in the longitudinal direction, are provided. Expediently, the guide faces are distributed circumferentially to the displacement axis over a region of more than 180xc2x0, so that they can absorb bending forces in all directions. For that purpose, guide faces that are located on the side walls of the coupling part can be utilized.
To make the fastening part pivotable about a longitudinal axis, the guide faces comprise parts of the jacket faces of bodies generated by rotation that are coaxial with the displacement axis, and the displacement axis expediently extends inside the coupling rod. Since the approach angle of the wiper strip is meant to be changed by the displacement, it is advantageous if the displacement axis extends as parallel as possible to an associated wiper blade. The vertical position of the wiper arm, and in particular the vertical position of the fastening part, in the region of the foldaway hinge, to the windshield should not vary, or should vary only slightly. This is achieved by providing that the displacement axis intersects the hinge axis of the foldaway hinge, or has the slightest possible spacing from the hinge axis.
The fastening part expediently surrounds the coupling rod with a U-shaped profile open toward the coupling rod and is connected to the coupling rod between the hinges, at the transverse wall of the U-shaped profile. The U-shaped profile is resistant to bending and allows a wide variety of variation, so that guide faces can be disposed over a large area between the coupling part and the fastening part. In the region of the fastening position, the transverse wall of the U-shaped profile of the fastening part has a bulge toward the open side of the U shaped profile, and this bulge engages a corresponding indentation of the coupling rod. The opposed walls of the bulge and indentation are designed such that they allow a displacement. They can also be called guide faces.
Fastening elements in the form of screws, screw nuts, threaded bolts and threaded stubs find space in the bulge without protruding past the outer contour of the fastening part. As a result, in a further feature of the invention, a cap, preferably of plastic, can cover the fastening position by being slipped onto the coupling rod. This averts the risk that in the motion of the coupling rod, parts will become caught between it and the levers pivotably connected to it. For reasons of appearance and streamlining, it is expedient that the fastening part, in the region of the connection point of the cap, has a step which is approximately equivalent to the thickness of the material of the cap, so that the outer contour of the cap adjoins the outer contour of the fastening part flush with it.
The adjustment serves the purpose above all of correcting for production tolerances. To prevent the fastening part from being roughly assembled wrong or shifting arbitrarily if the screw fastening should come loose, it is expedient that the displacement region is limited, for instance to an angular range of less than 5xc2x0, and preferably to 3xc2x0. This purpose is served by stops between the fastening part and the coupling rod, or between the elements that are solidly connected to these parts.
To enable an infinitely graduated displacement, the guide faces are smooth, or for better frictional engagement are roughened. By means of a fluting in the longitudinal direction parallel to the displacement axis, an incremental displaceability is attained. This is advantageous so that the adjustment from an outset position can be done in defined angular increments.